Suppose we know that 10% of all hypertensive patients who are given a placebo will have their DBP lowered by 10 mm Hg after 1 month. Can we carry out some procedure to be sure we are not simply observing the placebo effect?

Hypertension

Suppose 100 hypertensive people are given an antihypertensive drug and the drug is effective in 20 of them. By effective, we mean their DBP is lowered by at least 10 mm Hg as judged from a repeat blood-pressure measurement 1 month after taking the drug.